In the related art, pulse shower devices, which intermittently discharge water in pulses from shower holes by intermittently blocking and opening the shower holes, are well-known.
General pulse shower device's include a water dispersion plate including a plurality of shower holes that are provided from an inner surface to an outer surface, and an impeller that is provided on an upstream side of the inner surface of the water dispersion plate and rotates around an axis due to a water stream hitting vanes. The impeller includes, alternately in the circumferential direction, a shower hole blocking portion that extends over a predetermined circumferential length along the inner surface of the water dispersion plate in a downstream portion of an inner surface portion of the water dispersion plate and covers the shower holes, and as shower hole opening portion that opens toward the inner surface of the water dispersion plate.
In the above pulse shower devices, the shower hole blocking portion and the shower hole opening portion are rotationally moved around the axis through the rotation of the impeller, the shower holes are intermittently blocked and opened, and water is intermittently discharged in pulses from the shower holes.
For example, the following Patent Document 1 discloses a shower head including a cap (water dispersion plate) 70 having jet holes (shower holes) 74, and an impeller 56 on an upstream side of the cap. The impeller 56 includes a cover plate 60 as a shower hole blocking portion over a semicircle, and a shower hole opening portion over the remaining semicircle. The impeller 56 is rotationally moved by the action of a water stream to vanes 57, the cover plate 60 as the shower hole blocking portion and the shower hole opening portion are rotationally driven around an axis, the shower holes are intermittently blocked and opened, and water is intermittently discharged in pulses.
Additionally, the following Patent Document 2 discloses a water discharge device including a water dispersion plate 58 having shower holes 118, and an impeller 124 on an upstream side of the cover dispersion plate. The impeller 124 includes a shower hole blocking portion 130 over a semicircle, and a shower hole opening portion over the remaining semicircle. The shower hole blocking portion 130 and the shower hole opening portion are rotationally moved around an axis through the rotation of the impeller 124, the shower holes 118 are intermittently blocked and opened, and water is intermittently discharged in pulses.
In either of Patent Document 1 and Patent Document 2, a portion used as the water dispersion plate of a pulse shower device (device that intermittently discharges water through the rotation of the impeller) is only a portion on the inner peripheral side of the entire water dispersion plate of the shower head, the water dispersion plate (specifically, the portion used as the shower device in detail) and the impeller have smaller diameters, and the pulse shower device itself is small-sized.
In contrast, when the pulse shower device is enlarged, for example, when the entire larger-diameter water dispersion plate of the shower head up to an outer peripheral portion thereof is used as the water dispersion plate of the pulse shower device, the impeller is made to have a larger diameter with an increase in the diameter of the water dispersion plate, and thereby, when the pulse shower device is enlarged, a sensation while showering in water deteriorates if the shape of the small (small-diameter) impeller is merely made large (made to have a larger diameter) as it is.
For example, when the shape of a small-diameter impeller in which a half peripheral portion is formed as the shower hole blocking portion and the remaining half peripheral portion is formed as the shower hole opening portion is made to have a larger diameter as it is, a user feels that showering, in a shower has worsened. Specifically, a pulsating sensation of the water that is intermittently discharged becomes strong.
This is considered to be based on the following reasons. Hereinafter, descriptions will be made with reference to schematic views of FIGS. 13A and 13B.
In FIG. 13A, a small-sized pulse shower device 205A includes a small-diameter impeller 200A, a shower hole blocking portion 202A and a shower hole opening portion 204A that are provided in the impeller 200A, and water spray holes 206 provided in a water dispersion plate.
In FIG. 13B, in a large-sized pulse shower device 205B, a larger-diameter impeller 200B includes as shower hole blocking portion 202B and a shower hole opening portion 204B that are provided in the impeller 200B, and water spray holes 206 provided in a water dispersion plate.
In the small-sized pulse shower device 205A, attention is paid to shower holes 206a that are in a blocked state due to the shower hole blocking portion 202A. The shower holes 206a are brought into the blocked state for t1 seconds during the rotation of the impeller 200A, and are brought into an open state for t2 seconds (t1=t2) after that.
The same applies to shower holes 206a of the inner peripheral portion of the large-sized pulse shower device 205B. That, is the time for which the shower holes are brought into the blocked state by the shower hole blocking portion 202B is t1 seconds, and the time for which the shower holes are brought into the open state by the shower hole opening portion 204B is t2 seconds.
If attention is paid to shower holes 206b and 206c of the outer peripheral portion of the large-sized pulse shower device 205B, the circumferential length of the outer peripheral portion of the shower hole blocking portion 202B that acts to block the shower holes 206b and 206c is greater than the circumferential length of the shower hole blocking portion 202A in the small-sized pulse shower device 205A. Nevertheless, the time for which the shower holes are brought into the blocked state by the shower hole blocking portion 204B is t1 seconds, and the time for which the shower holes are brought into the open state by the shower hole opening portion 204B is t2 seconds. That is, this is the same as in the case of the shower holes 206a. 
If both of the rotational frequency of the impeller 200A of the small-sized pulse shower device 205A and the rotational frequency of the impeller 200B of the large-sized pulse shower device 205B are both n1, only the circumferential speed of the portion on the outer peripheral side of the shower hole blocking portion 202B becomes faster than the circumferential speed of the shower hole blocking portion 202A, but the rotating speeds (the rotational frequencies) are the same. Therefore, the time interval it takes until the shower holes are brought into the open state from the blocked state and brought into the blocked state from the open state are the same not only in the shower hole 206a but also in the shower holes 206b and 206c. 
Nevertheless, in the case of the large-sized pulse shower device 205B, a user feels that the time interval taken until the water is switched from being blocked to being able to flow freely and from being able to flow freely to being blocked is physically felt as being longer, a pulsating sensation is strong, and a user's sensation while showering in water deteriorates.
The following reason is mentioned as one reason. That is, even if the positions of the holes from which water flow out vary in the portion of the water dispersion plate on the inner peripheral side, all the shower holes are in a small area of the inner peripheral portion. Therefore, a user does not feel the variation very strongly in terms of physical sensation. Meanwhile, in the portion on the outer peripheral side, an area in which the shower holes are present is large, and the number of shower holes is also large. Therefore, a poor distribution between each of a region from which water flow out and a region from which water does not flow out is strong. Therefore, a strong movement of the region from which shower flow out and the region from which water does not flow out is felt, and this leads to a strong pulsating sensation of water.
In the pulse shower devices that intermittently discharge water, it is necessary to give a pulsating sensation. On the other hand, a too strong pulsating sensation deteriorates the showering feeling. Therefore, there is demand for improvement.